A pump housing for a rotary pump

Abstract: The invention concerns a pump housing (1) for a vortex-flow pump. The housing (1) is divided into a cylindric lower part (6) and a spiral upper part (7).

Description: The invention concerns pumps which shall be able to operate totally or partly submersed into the pumped medium, the latter often containing large amounts of solid bodies. Examples are water on construction sites and waste water. Within the fields mentioned above the so-called vortex-flow pump provides certain advantages over conventional centrifugal pumps, especially at small dimensions. A vortex-flow pump is characterized by the fact that the impeller is axially displaced in the pump housing as compared with a conventional centrifugal pump. This means that a wide free throughlet is obtained and thus the risk for clogging is often diminished. Accordingly it is then often possible to use smaller pumps for pumping heavily polluted liquids and thus the costs can be reduced. The fact that a vortex impeller is simpler to manufacture than a centrifugal impeller further decreases the costs. An example is shown in US - A - 37 596 28. The vortex-flow pump has however certain disadvantages. The efficiency is often lower as compared with a conventional centrifugal pump. The head often becomes lower even at small volume flows and in addition the power demand rises rapidly at increasing volume flow. The purpose of the invention is thus to increase the efficiency and to increase the possible head, especially at small volume flows. This is obtained by help of the device stated in the claims. The invention is described below with reference to the enclosed drawings. Fig 1 shows a side view of a conventional vortex-flow pump, Fig 2 shows a side view of a pump housing according to the invention, while Fig 3 shows a number of cuts through the pump housing showing the volume increase of the volute. In the drawings 1 stands for a pump housing having inlet 2 and outlet 3. 4 stands for a pump impeller having vanes 5. 6 stands for a cylinder formed part of the pump housing, 7 a spiral part having an outer wall 8 and a lower wall 9. 10, 11 and 12 stand for cuts through the wall at different points around the circumference. With reference to Fig 1 the operation of a conventional vortex-flow pump is described. The liquid is sucked in axially through the inlet 2 and is thrown towards the circumference by the impeller vanes 5 on the impeller 4 and is finally pushed out through the outlet 3. The room between the bottom of the housing and the impeller vanes has a certain minimum dimension which is decided by state authorities when waste water is pumped. This in order to ensure that solid bodies up to a certain dimension shall be able to pass through the pump without being blocked. The disadvantage caused by said room is that eddies occur which bring back a part of the liquid to the center and in addition check the rotation of the impeller and increase the risks for cavitation and vibrations. The Swedish Patent No 462 869 shows a pump where the problems are said to be solved by providing the impeller vanes with deflection means which shall prevent the liquid from flowing back to the center. A problem with this solution is however that the risks of clogging increase. Another previously mentioned disadvantage with the vortex-flow pumps is the strong increase of power demand at increasing volume flow. A known device to diminish this risk is shown in the Swedish patent No 374 415 where the pump housing is provided with elastic parts which choke the throughlet at certain pressure conditions. According to the invention the pump housing is designed with a circular part 6 adjacent the inlet and a spiral part 7 remote from said inlet. The circular part 6 is designed in a conventional manner and provides the prescribed free throughlet between the bottom of the housing and the impeller 4. The spiral part 7 is designed like a volute where the radius of the outer wall 8 increases continously from a minimum corresponding with the radius of the cylindric part 6 to a maximum at the outlet 3. In a corresponding way the height or the axial extension of the volute increases in the direction of the outlet as shown in Fig 3. The height of the cylindric part 6 decreases correspondingly. The advantage to design one part of the pump housing like a volute is that the lower wall 9 of said volute prevents a part of the return flow to the cylindric part 6. Instead it forces a greater amount of liquid to remain in the spiral part 7 to be pushed towards the outlet 3. This decreases the losses to a great extent. An additional advantage with the volute is that a considerable pressure increase at small volume flows can be obtained by help of the flow concentration that the volute obtains. In a corresponding way the volute brings about that the power demand at increasing volume flow sometimes can be limited as compared with conventional vortex-flow pumps with totally cylindrically formed housing.

Claims: A pump housing of the so-called vortex-flow type provided with an impeller (4) with vanes (5), an axial inlet (2) and a tangential to radial outlet (3), characterized in that the part (6) where the inlet (2) is located is essentially circular with an increased diameter as compared with that of the inlet (2) and that the impeller (4) is located in the part (7) of the housing located remote from the inlet (2), said latter part (7) being designed like a volute having a continously increasing radius in the direction of the outlet (3). A pump housing according to claim 1, characterized in that the smallest diameter of the volute (7) corresponds with the diameter of the circular part (6).

Inventors: BORG TOROLF, STRINNING PER E, BORG, TOROLF, STRINNING, PER E.
Applicants: FLYGT AB ITT, ITT FLYGT AB
Application year: 1994
Main classification: F04D7
IPC codes: F04D5, F04D7, F04D29